The present invention relates to a pneumatic tire having an improved carcass profile in the bead portions capable of improving the steering stability, road noise and the like.
Recently, in order to solve an environmental problem, there is a strong demand for tires capable of decreasing the fuel consumption of automobiles. Therefore, it is taken as a countermeasure therefor to reduce the tire weight by decreasing the number of reinforcing cord layers and/or the thickness, size or volume of rubber components. In such countermeasure, however, it is almost inevitable that the tire rigidity, especially lateral stiffness is decreased. Accordingly, the cornering power decreases and as a result, it is difficult to improve the steering stability.
It is therefore, an object of the present invention to provide a pneumatic tire in which the lateral stiffness can be improved without providing additional reinforcing layers and without increasing the sizes of the existing reinforcing layers and rubber components so as not increase the tire weight.
According to the present invention, a pneumatic tire comprises a pair of axially spaced bead portions with a bead core therein, and a carcass comprising a main portion extending from one of the bead cores to the other, wherein
in a state that the tire is mounted on a standard rim and inflated to a standard pressure but loaded with no tire load, a carcass line inclination angle .alpha. is not more than 20 degrees, wherein PA1 the carcass line inclination angle .alpha. is defined as an angle with respect to the tire radial direction, of a straight line (X) drawn between a first point (P1) and a second point (P2), PA1 the carcass line is a thickness center line of the carcass main portion, PA1 the first point (P1) is an intersecting point between an axial line (K2) passing a bead heel point and a tangent to the carcass line at a radial height of the radial center of the bead core, and PA1 the second point (P2) is a point on the carcass line at a radial height of a flange of the standard rim.